The present invention relates to a data recording apparatus such as an optical disk apparatus for recording/reproducing image data.
An optical disk apparatus optically records data on or reproduces it from an optical disk by scanning the rotating optical disk with a laser beam. The optical disk receives great attention as a large-capacity memory which has never been proposed. For example, the optical disk can be applied to a large-capacity image file apparatus.
One of the optical disk apparatus of the type described above uses an optical disk with a spiral pregroove or concentric pregrooves, each of which is an array of prepits. A reproducing laser beam and an intense recording laser beam alternately illuminate the pregroove while the disk is rotating. The reproducing laser beam tracks the pregroove, and the recording beam cuts data pits in the pregroove, thus recording image data on the disk. A semiconductor laser diode keeps emitting a less intense reproducing beam, thereby tracking the pregroove all the time during the operation of the disk apparatus. When a beam modulating signal (i.e. recording pulse having a width of less than several hundred nanoseconds) is supplied to the laser diode, the laser oscillator emits an intense recording beam for the period of time equal to the width of the recording pulse. The recording beam illuminates the pregroove and cuts a data pit in the pregroove.
The data recording on the optical disk may be deteriorated with time and may eventually be destroyed. In order to record new image data in that portion of the pregroove which has not been used, an optical head including the semiconductor laser diode must be brought to the starting track or the last recorded track (i.e. "-1 track"), or the recording end address. If the tracking data previously recorded have been destroyed or distorted, a tracking error is unavoidable. Due to the tracking error the optical head cannot be moved to the starting track or the -1 track.
Furthermore, in the optical disk apparatus described above, a tracking error tends to occur when a strong impact is applied on the apparatus while the optical head is recording data on a nonrecorded area of the disk. The laser beam is then incident on the track on which data is already recorded, thus resulting in overlay recording.